Morphology Of Nanotubes Research Articles

Hierarchical Nanotube Self‐Assembly of DNA Minor Groove‐Binding Ligand DB921 via Alkali Halide Triggering

A systematic study into a novel self‐assembling system is presented whereby the small molecule DB921 forms nearly monodisperse nanotubes upon addition of a suitable salt. Small‐angle X‐ray scattering and negative stain transmission electron microscopy are employed as the principal characterization methods to study both the fundamental assembly processes and reaction kinetics. The assembly is found to be hierarchical, culminating with helical winding of intermediate ribbon structures into nanotubes. The driving force for this process is likely the electrostatic interaction between DB921 and salt anions; this aspect can be used to control nanotube assembly and morphology.

Electric-field-induced microstructure modulation of carbon nanotubes for high-performance supercapacitors

The growth direction, morphology and microstructure of carbon nanotubes (CNTs) play key roles for their potential applications in electronic and energy storage devices. However, effective synthesis of CNTs in high crystallinity and desired microstructure still remains a tremendous challenge. Here we introduce an electric field for controlling the microstructure formation of CNTs. It reveals that the electric field not only make CNTs aligned parallel but also improve the density of CNTs. Especially, the microstructures of CNTs gradually change under electrical field. That is, graphite sheets are transformed from the “herringbone” structure to a highly crystalline structure, facilitating the transportation of electrons. Due to the improved aligned growth direction, high density and highly crystalline microstructure, the electrochemical performance of CNTs is greatly improved. When the CNTs are applied in supercapacitors, they present a high specific capacitance of 237 F/g, three times higher than that of the CNTs prepared without electrical field. Such microstructure modulation of CNTs by electric field would help to construct high performance electronic and energy storage devices.

Anodization growth of TiO2 nanotubes on Ti–35Nb–7Zr–5Ta alloy: effects of anodization time, strain hardening, and crystallographic texture

Titanium and its alloys are the most suitable metallic materials available for the fabrication of medical implants. Their biocompatibility can be improved by the growth of TiO2 nanotubes on their surface by a simple anodization process. This work involved an investigation into the anodization behavior of Ti–35Nb–7Zr–5Ta (TNZT) alloy, focusing on the effect of processing conditions (anodization time and type of electrolyte), previous strain hardening, and crystallographic texture of the substrate. Studies about the growth of TiO2 nanotubes on β-type titanium alloys, as the TNZT alloy, are rare in the literature. The TNZT alloy proved to be an excellent substrate for the growth of TiO2 nanotubes, resulting in threefold longer nanotubes than those obtained on a commercially pure (CP) Ti substrate. Moreover, TiO2 nanowires grew after 6 h of anodization in an organic electrolyte, which could not be achieved using the CP-Ti substrate. Samples with different crystallographic textures displayed similar nanotube morphology and only slight differences in grain length, indicating that grain orientation played only a minor role in the growth kinetics. Lastly, the crystallization of nanotubes at 450 °C did not alter their morphology, but caused complete detachment of the TiO2 nanotubes at 700 °C.

The efficiency of TiO2 nanotube photoanode with graphene nanoplatelets as counter electrode for a dye-sensitised solar cell

Dye-sensitised solar cells (DSSCs) have been widely studied since their discovery; however, a number of problems should be solved to enhance their efficiency. We successfully fabricate Titanium oxide nanotubes on the Ti foil as photoelectrodes to improve the power conversion efficiency of DSSCs by an anodising method under the influence of ultrasound wave. The morphology and structure of TiO2 nanotubes were characterised by the atomic force microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The results confirmed a good array of TiO2 nanotubes on the Ti substrate at 30 min, the significantly improved output of DSSC, and the power conversion efficiency of 0.26 for enhancing the photovoltaic performance.

Hydrothermal synthesis and characterization of vanadium-doped titanium dioxide nanotubes

Undoped and vanadium (V)-doped titanium dioxide nanotubes (TNTs and VTNTs, respectively) were synthesized by hydrothermal method for biological applications. The fabricated nanotubes were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, nitrogen adsorption-desorption isotherms, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The XRD and vibrational spectra results showed as-prepared nanotubes were complete anatase phase. The characterization of the morphology of the as-obtained nanotubes reveals that the samples are tubular in shape and the starting spherical titanium particles were fully transformed into a tubular material. The TEM and SEM results are in good agreement with XRD, FT-IR, and Raman analysis. The purpose of this study is to produce and characterize the vanadium-doped titanium dioxide nanotubes, such that this material can be employed for biomedical applications. TEM and SEM findings cleared that vanadium doping does not affect significantly the structure of titanium dioxide nanotubes which are uniform and compact.

A novel morphology of 3D graphene hydrogel nanotubes for high-performance nonenzymatic hydrogen peroxide sensor

A novel nanostructure of three-dimensional graphene hydrogel nanotubes (3DGHNTs) is successfully synthesized for the purpose of sensing non-enzymatic H2O2 in alkaline solution. The 3DGHNTs were fabricated using manganese dioxide nanotubes (MnO2 NTs) as the effective sacrificial template and without the use of any acids or a high temperature process. 3DGH with different percentages of MnO2 NTs ranging from 5 to 30% are prepared via a hydrothermal method. When the loading percentage of MnO2 NTs is 10%, the obtained 3DGHNTs-Mn10 nanocomposite exhibits a large specific surface area with high porosity, which enhance the electrochemical properties for H2O2 detection. The developed biosensor exhibits excellent sensitivity (220.4μAmM−1cm−2) with a wide linear detection range (25μM–22.57mM) and a low detection limit (4μM). The biosensor also shows a fast response time (less than 5s) and good selectivity as well as reproducibility and long-term stability. Hence, the prepared 3DGHNTs-Mn10 nanocomposite can be considered a promising electrode material for the detection of H2O2 in real sample.

Electrocatalytic reduction of nitrobenzene using TiO2 nanotube electrodes with different morphologies: Kinetics, mechanism, and degradation pathways

Here we report on one of the first studies utilizing self-doped TiO2 nanotube arrays (NTAs) for electrocatalytic reduction of water pollutants with nitrobenzene (NB) as the model compound. In particular, we focused on the effects of morphological and crystallographic characteristics on the electrochemical reactivity of TiO2 NTAs towards the target pollutant. The TiO2 NTAs with different morphologies and exposed facets were synthesized by tuning a suite of anodization parameters and applying a post-anodization treatment. A series of electrochemical reduction tests using TiO2 NTAs as the cathode were carried out to investigate the effects of nanotube morphologies and operating conditions. Results indicate that the {0 0 1}-exposed facet, longer nanotube length, and larger nanotube diameter are the structural and morphological features that can lead to enhanced performance of TiO2 NTA electrodes. With the applied cathode potential of −1.20 V/SCE and an initial concentration of 300 mg/L, >95% NB can be efficiently degraded at the energy consumption of 2.07 kWh/m3 (EE/O), 7.67 kWh/kg (NB), and 30 kWh/kg (C), all of which are much lower than those of electrochemical oxidation processes. The good stability of the TiO2 NTA cathode was also demonstrated in 10 cyclic runs. Furthermore, CV measurements and scavenger tests were employed to study the reaction mechanism. It was found that both the direct reduction and surface adsorbed H* contributed to NB degradation. The NB transformation pathway and degradation kinetics of NB and the intermediate products were also investigated. Results obtained from this study suggest that the self-doped TiO2 NTA is a promising cost-effective electrode material for electrocatalytic reduction of water pollutants with high efficiency and stability.

Controlled synthesis of vertically aligned honeycomb TiO2 nanotube arrays: effect of high-temperature annealing on physical properties

Vertically aligned honeycomb titania (TiO2) nanotube arrays grown on Ti foil were synthesized by electrochemical anodization method. The changing of morphology, crystalline structural, and optical properties of anodic titania nanotube (ATNT) arrays systematically studied. A novel annealing approach is proposed to retain the ATNT arrays at high temperatures ranging from 700 to 900 °C. At 700 and 800 °C, FESEM images showed that the nanotubular structures were preserved from annihilation and the morphology of the structure was a mixture between anatase and rutile. However, the highlight of this research was the successful synthesis of the high-quality rutile ATNT arrays at 900 °C. The X-ray diffractometer measurements proved that the variations in the mean crystallite sizes of anatase and rutile phase occurred during annealing of ATNT samples. The corresponding optical bandgaps were determined by extracting the reflectance values and combining Kubelka–Munk function with the indirect Tauc plot for transition phases of ATNT arrays for high-temperature annealed films.

Preparation effects on the morphology and photocatalytic properties of carbon nitride nanotubes

Abstract Water reduction to hydrogen (H2) by solar light is a green and sustainable approach to solve the energy crisis. However, conventional semiconductors usually suffer from low light absorbance and high charge recombination rate, which largely suppressed the application of this technology. Here, carbon nitride nanotubes (C3N4 NTs) prepared via morphological transformation method were utilized as photocatalysts for H2 production. The dispersed C3N4 nanosheets with few layers, suitable temperature difference and heating atmosphere in the process are of great importance to the formation of well-structured nanotubes. The C3N4 NTs demonstrates high visible light absorbance and efficient charge transfer kinetics, as evidenced by the UV–vis diffuse reflectance and photoluminescence spectra. In the absence of cocatalysts, a H2 generation rate of 2.69 µmol·h−1·mg−1 was achieved with an apparent quantum efficiency of 2.16% at 420 nm wavelength.

Preparation and characterization of TiO2 nanotubes antimicrobial coating of iodine-supported titanium implants

TiO2 nanotubes have a good application prospect in the field of drug load and delivery. In this study, TiO2 nanotubes were prepared by electrochemical anodic oxidation with voltage and time of 60 V and 2 hours, respectively. After anodization, it was annealed at 450 ° C for 2 hours. The crystalline phases as well as the morphology and structure of nanotubes were characterized by XRD, field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The results show that surface of TiO2 nanotubes are clean and highly ordered construction. In addition, the diameter and wall thickness of the nanotubes are about 110 nm and 5 μm, respectively. Finally, the TiO2 nanotubes which load iodine by electrodeposition method have polymer particulate iodine on the surface, thereby developed a kind of orthopaedic implants with antibacterial properties, which is expected to be widely used in clinical practice.

Ta3N5/Co(OH)x composites as photocatalysts for photoelectrochemical water splitting.

Ta3N5 nanotubes (NTs) were obtained from nitridation of Ta2O5 NTs, which were grown directly on Ta foil through a 2-step anodization procedure. With Co(OH)x decoration, a photocurrent density as high as 2.3 mA cm-2 (1.23 V vs. NHE) was reached under AM1.5G simulated solar light; however, the electrode suffered from photocorrosion. More stable photoelectrochemical (PEC) performance was achieved by first loading Co(OH)x, followed by loading cobalt phosphate (Co-Pi) as double co-catalysts. The Co(OH)x/Co-Pi double co-catalysts may act as a hole storage layer that slows down the photocorrosion caused by the accumulated holes on the surface of the electrode. A "waggling" appearance close to the "mouth" of Ta2O5 NTs was observed, and may indicate structural instability of the "mouth" region, which breaks into segments after nitridation and forms a top layer of broken Ta3N5 NTs. A unique mesoporous structure of the walls of the Ta3N5 NTs, which is reported here the first time, is also a result of the nitridation process. We believe that the mesoporous structure makes it difficult for the nanotubes to be fully covered by the co-catalyst layer, hence rationalizing the remaining degradation by photocorrosion.

Effect of carbon nanotube morphology on properties in thermoplastic elastomer composites for strain sensors

Electrically conductive thermoplastic polyurethane (TPU) composites with carbon nanofillers have potential applications in strain sensors. However, it is challenging to simultaneously achieve low percolation threshold, good electrical conductivity and high strain sensitivity especially in melt-mixed TPU-carbon filler nanocomposites. Here, we report on using branched carbon nanotubes known as carbon nanostructures (CNS) in melt-mixed TPU composites. These composites have an electrical percolation threshold (ΦC) of 0.82 wt%, whereas when using multiwall carbon nanotubes (CNT) the ΦC is 3.02 wt%. Based on linear fitting, the TPU nanocomposite with 2 wt% CNS shows gauge factors of 15, 30 and 58 for strain levels of 0–44%, 45–73% and 74–100%, respectively, by comparison with the 5 wt% CNT nanocomposite, which exhibits a gauge factor of 18 for strain 0–100%. These composites show potential strain-sensing applications in detection of joint bending and muscle exercise. This study reveals the effects of CNT morphology on polymer composite properties, enhancing the understanding of structure-property relationship for polymer nanocomposites.

Biomimetic Hydroxyapatite a Potential Universal Nanocarrier for Cellular Internalization & Drug Delivery.

Functional biomaterials can be used as drug loading devices, components for tissue engineering or as biological probes. As such, the design, synthesis and evaluation of a variety of local-drug delivery structures has been undertaken over the past few decades with the ultimate aim of providing materials that can encapsulate a diverse array of drugs (in terms of their sizes, chemical compositions and chemical natures (i.e. hydrophilic/hydrophobic). Presented here is the evaluation of specifically hollow 1D structures consisting of nanotubes (NTs) of HAp and their efficacy for cellular internalization using two distinguished anti-cancer model drugs: Paclitaxel (hydrophobic) and Doxorubicin hydrochloride (hydrophilic). Importantly, it has been observed through this work that HAp NTs consistently showed not only higher drug loading capacity as compared to HAp nanospheres (NSs) but also had better efficacy with respect to cell internalization/encapsulation. The highly porous structure, with large surface area of nanotube morphology, gave the advantage of targeted delivery due to its high drug loading and retention capacity. This was done using the very simple techniques of physical adsorption to load the drug/dye molecules and therefore this can be universally applied to a diverse array of molecules. Our synthesized nanocarrier can be widely employed in biomedical applications due to its bio-compatible, bio-active and biodegradable properties and as such can be considered to be a universal carrier. Graphical Abstract Schematic representation for a comparative study of hydroxyapatite (hollow nanotubes vs solid nanospheres) with variety of drug/ dye molecules.

Modification of carbon nanotubes by an ion beam of argon

By Scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy has been studied the effect of an argon ion beam with energy of 5 keV and various fluences (1·1016 and 5·1016 ion/cm2) on the morphology, structure, and chemical state of multi-walled carbon nanotubes (MWCNTs). It has been established that irradiation of MWCNTs with argon ions leads to the formation of structural defects and functional oxygen-containing groups of various types (hydroxyl, carboxyl / carbonyl, ether, etc.). It is shown that an increase in the fluence of the beam leads to an increase in the number of functional groups fixed on the walls of the MWCNTs, without changing the types of oxygen-containing groups. It is shown that modification by ion-beam action is promising for increasing the chemical activity and changing the electronic properties of the outer walls of MWCNTs.

The Structure and Electrophysical Properties of Multiwall Carbon Nanotubes Subjected to Argon Ion Bombardment

The morphology, structure, and electrophysical characteristics of multiwall carbon nanotubes (MWCNTs), as affected by defects induced by ion bombardment, are studied using Raman spectroscopy and scanning and transmission electron microscopies. Annealing in an inert atmosphere results in partial recovery of the nanotube structure: the nanotube walls contain regions of recovered graphene structure and regions plagued with extended defects that result in corrugation of graphene layers comprising the walls of MWCNTs. These structural alterations result in a marked decrease in conductivity of the processed MWCNTs.

Plasma-Induced Crystallization of TiO₂ Nanotubes.

Facile crystallization of titanium oxide (TiO2) nanotubes (NTs), synthesized by electrochemical anodization, with low pressure non-thermal oxygen plasma is reported. The influence of plasma processing conditions on TiO2 NTs crystal structure and morphology was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the first time we report the transition of amorphous TiO2 NTs to anatase and rutile crystal structures upon treatment with highly reactive oxygen plasma. This crystallization process has a strong advantage over the conventional heat treatments as it enables rapid crystallization of the surface. Thus the crystalline structure of NTs is obtained in a few seconds of treatment and it does not disrupt the NTs’ morphology. Such a crystallization approach is especially suitable for medical applications in which stable crystallized nanotubular morphology is desired. The last part of the study thus deals with in vitro biological response of whole blood to the TiO2 NTs. The results indicate that application of such surfaces for blood connecting devices is prospective, as practically no platelet adhesion or activation on crystallized TiO2 NTs surfaces was observed.

A Molybdenum Carbide Nanotubes Modified Electrode as the Functionalized Sensing Platform for Electrochemical Detection of Dopamine

AbstractIn this work, molybdenum carbide (Mo2C) nanotubes were prepared via the self‐degradable template method and high‐temperature calcination, and then were successfully used to modify glassy carbon electrode (CGE) for the high‐sensitivity determination of dopamine (DA) without the inference of ascorbic acid(AA) and uric acid (UA). The surface morphology of Mo2C nanotubes has been investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). Owing to the enhanced electron transfer rate and high surface area of Mo2C, the modified electrode not only exhibits very excellent electrochemical performance for DA, but also has good analytical performance for DA in the mixture with AA and UA through differential pulse voltammetry (DPV), which can be applied for DA detection with wide linear range(0.005–50 μmol L−1) and low detection limit 0.001 μmol L−1. The modified electrode has been applied to detect DA in DA hydrochloride injection by using standard adding method with satisfactory results.

The Dependence of the Aggregate Stability to Concrete of Modifying Additives Based on Halloysite Nanotubes in Water Environment on the Character of the Stabilizer

The stabilizer nature effect on the aggregative stability of the modifying concrete additives based on halloysite nanotubes in the aquatic environment is shown. The chemical composition and morphology of halloysite nanotubes and their additives, obtained by ultrasonic dispersion in the aquatic environment of the surfactant, are studied. The influence on the processes of charge stabilization on the outer and inner surface of halloysite nanotubes is determined. The dependence of nanotube sizes and specific surface area on the stabilizer type, the time of ultrasonic dispersion, and additive storage is revealed. The stabilization mechanisms of aqueous dispersions of modifying additives based on halloysite nanotubes with anion-and cation-active substances are considered. It is established that the polynaphthalenesulfonate-based modifier S-3 has got the maximum efficiency as a stabilizer of aqueous dispersions of modifying concrete additives with halloysite nanotubes.

Effect of Mo addition on the microstructure and catalytic performance Fe-Mo catalyst

Fe-Mo catalyst with different molar ratios (1:0, 1:0.5, 1:1, 1:2, 1:3) were prepared by chemical co-precipitation method, and they were added to phenolic resin as catalysts. The microstructure and physicochemical properties of catalyst and crystalline carbon after phenolic resin pyrolysis were characterized by XRD, SEM, FT-IR, XPS and TEM. The results showed that the Fe/Mo molar ratio played a significant role in the graphitization of phenolic resin and the morphology of carbon nanotubes. The graphitization of the phenolic resin first increased and then decreased with the addition of Mo. When the Fe/Mo molar ratio was 1:2, the phenolic resin achieved the highest graphitization, and the formed carbon nanotubes had the highest crystallinity. The Fe atoms were in an electron-deficient state due to the electrons transferring from Fe to Mo, which enhanced the hydrocarbon compounds absorption on the surface of catalyst. And Mo was carbonized by carbon atoms to form α-MoC1-x, and then decomposed into β-Mo2C and graphite carbon, obtaining carbon atoms orderly arrangement and carbon nanotubes. Therefore, both the grain size and electron structure of catalyst significantly affect the catalytic properties of Fe-based catalyst.

Microstructure characterization of biocompatible heterojunction hydrogen titanate-Ag2O nanocomposites for superior visible light photocatalysis and antibacterial activity

Hydrogen trititanate (H2Ti3O7·2H2O) and hydrogen trititanate/Ag2O hybrid nanocomposites (NCs) with novel structure have been synthesized by a simple solvothermal route followed by Na+/H+ ion-exchange. Growths of hydrogen trititanate with nanofiber (HTNF) and nanotube (HTNT) morphologies and hydrogen trititanate-Ag2O (HTFAG and HTTAG) nanocomposites have been tailored by controlling the solvent media. Detailed microstructure characterization of all these samples have been carried out by Rietveld refinement of XRD data and analyzing FESEM/HRTEM micrographs and FTIR spectra. Band gap energies of all these semiconducting samples are obtained from UV–Vis absorption spectra. Both HTFAG and HTTAG NCs exhibit enhanced photocatalytic degradation of organic pollutant (Congo red dye) under visible light, in comparison to HTNF and HTNT respectively due to the formation of a heterojunction between H2Ti3O7·2H2O and Ag2O, which is supported by photoluminescence spectroscopy. HTFAG and HTTAG NCs also show superior antibacterial activity against both gram-negative (Escherichia coli) and gram-positive (Bacillus subtilis) bacteria compared to their pure counterparts. MTT assay reflects a sufficiently high percentage of cell viability and confirms the significant cytocompatibility of all the samples.